In the process of tungsten carbide injection molding, the structure of the preform has a certain influence on the solvent debinding process. It includes two factors: the thickness of the preform and the shape of the preform. The essential effect of preform structure on debinding rate is the effect of sample thickness and sample surface area.

 

The removal rate is proportional to the surface area of green, and is inversely proportional to the thickness. When the sample thickness is smaller, the surface area will be larger and the solvent debinding rate will be greater.

 

1, Effect of Preform Thickness on Solvent Debinding of Tungsten Carbide

From the above figure, in the same degreasing time, with the increase of the sample thickness, the degreasing rate decreases, and with the increase of the sample thickness, the decrease is more and more big. In the forming blank, the binder uniformly wraps the powder and forms a connected network.

 

 

When a part of the binder is removed, the place becomes the pore, and the removed binder is transferred to the surface along these pores. The distance between the binder and the solvent to the solvent is much larger than the distance from the sample to the surface of the sample. With the increase of the sample thickness, the longer the distance of the binder diffusion to the sample surface, the longer the time required to achieve the same degreasing rate.

 

Especially, because of the irregular shape of tungsten carbide powder, the interconnected pores formed by the binder become more complex, and the diffusion process is more difficult. In addition, the solvent debinding process is often accompanied by swelling, which leads to an increase in the possibility of defects in the sample with the increase of the thickness.

 

2, Effects of Preform Shape on Degreasing Rate

The removal rate is proportional to the surface area of green and green, and is inversely proportional to the thickness. When the sample thickness is smaller, the surface area will be larger, and the solvent debinding rate will be greater.